1. Field of the Invention
The present invention relates to a method and an apparatus for controlling a plurality of automatic machining units provided at a plurality of machining stations of a transfer machine system, respectively.
2. Description of the Related Art
Japanese Examined Utility Model Publication No. 2-32370 discloses a transfer machine system that includes a plurality of unit control panels, each of which includes a sequence control circuit and a power supply, and a plurality of sub-console boxes, which can be operated by an operator in order to control the respective unit control panels. Each of the sequence control circuits is associated with a respective automatic machining unit and transmits an instruction signal to the corresponding machining unit according to a predetermined machining program.
The transfer machine system further includes a main control panel and a main control box as a host computer. The main control panel includes an internal programmable controller that instructs each unit control panel with a predetermined sequence control. The main control box permits the operator to control all the unit control panels via the main control panel. The individual sequence control circuits of the unit control panels are connected with the programmable controller, and data can be mutually transmitted therebetween. Therefore, each of the machining units can be individually controlled by means of the respective sub-control boxes. Further, all the machining units can be collectively controlled by means of the main control box.
In this conventional system, the main control panel gathers data or information transmitted from each of the machining units. The main control panel determines certain matters based on the gathered information, and transmits instructions to the individual unit control panels of the machining units. Therefore, the conventional system requires a relatively long period of time to perform determinations and transmissions of signals (including collecting information and transmitting instructions). This increases the cycle time period of the transfer machine.
The main control panel cannot determine whether the entire system is controllable or not, nor can it adjust the control conditions until all the machining units are set up. Therefore, the installation and the maintenance of the conventional system is troublesome. Furthermore, when some additional machining stations and units are combined with the conventional system, the control program stored in the main control panel must be changed. Therefore, the conventional system is not readily expandable.
Furthermore, according to the conventional system, when an operator collectively controls the machining units via the main control panel, the operator must move to the place where the main control box is located. The larger the system becomes, the more difficult it becomes for the operator to handle it.